1. Field of the Invention
The present invention relates to a piston for a compressor used, for example, in a vehicle air-conditioning system.
2. Description of the Related Art
Piston compressors are one type of compressor used in vehicle air-conditioning systems. Some of the pistons in such compressors are constructed with no piston ring, so that the outer perimeter side surface of the piston directly contacts the inner perimeter side surface of the cylinder bore. For pistons with this type of construction, it is necessary to guarantee sliding properties, seal properties and wear resistance between the outer perimeter side surface of the piston and the inner perimeter side surface of the cylinder bore, since no piston ring is provided.
It has been conventional to form a coat layer composed mainly of a fluorocarbon resin or the like on the outer perimeter side surface of the piston, in order to guarantee these sliding properties, seal properties and wear resistance (see, for example, Japanese Unexamined Patent Publication (Kokai) Nos. 9-256952, 10-26081, 10-169557 and 10-299654).
However, with the pistons of such conventional piston compressors that have a coat layer formed of a coating material composed mainly of a fluorocarbon resin, a problem has existed in that the wear resistance of the coat layer is not always satisfactory.
The present invention has been accomplished in light of these existent problems of the prior art, and its object is to provide a piston compressor piston that has a coat layer with excellent wear resistance.
The piston compressor piston according to the invention is a piston compressor piston having a coat layer provided on the outer perimeter side surface of the piston, which coat layer comprises a fluorocarbon resin and a binder at 50-400 parts by weight per 100 parts by weight of the fluorocarbon resin, and further contains a wear resistance additive with a Mohs hardness in a range of 2.0-5.0 at 0.05-12% by volume based on the fluorocarbon resin.